1979 Volvo MD-17c, it ain't broke so should I not touch it?

[Lou-In-NJ]

My raw-water cooled 3 cylinder Volvo MD-17c is 45 years old. I've owned it for about 6 years now and I average about 25 hours per season. I'm the second owner and I've done regular oil changes, water pump">raw water pump and thermostat maintenance. The engine fires up cold with about a 1-2 second fogging of starter fluid around the intake snorkels (but not in the snorkels); on a warm day, no ether is needed to fire the engine.
Here is a link to a video from a couple of weeks ago, showing the exhaust of the engine while it is running on the hard.
https://drive.google.com/file/d/1MFE...ew?usp=sharing

While there is smoke, it's mostly white and I attribute part of that to the anti-freeze I put through the engine; although the engine does smoke normally anyway, but it smells like diesel exhaust from a time before emissions requirements. Oil consumption is fairly low, about 1/2 quart after about 15 hours of use. So I'm thinking about doing a valve job with new springs, valves, guides and stem seals; and de-carbon of the exhaust system. Or maybe I do an upper engine rebuild, which would include new cylinder-liners, pistons and rings.

This work would all be in-vessel, which is one reason I probably wouldn't do the bottom end at this point; although with the engine half apart, I might just go all the way if I determine there is too much play on the big-ends of the connecting rods.

The other option is to simply pull the 3 injectors, send them for service (I've never done this, but it was done in the past judging by the missing paint on the injectors), and bore-scope the cylinders and see what I see.

I've always done all of my own engine work, and everything I've done has stood the test of time. I currently own a diesel powered car with 160k on it, and I just did glow plugs, including a fairly difficult extraction a one of them; so I'm typically undaunted by difficulties, but in the interest of time, if I were to do any of this work, I'd have to start with in the next two weeks to insure I'd have all the parts in, and machining work done, by April.

Any ideas and suggestions from anyone knowledgeable, on any aspect of this, including my exhaust, are welcome.

[Rucksta]

Check the availability of injectors and service parts before making a decision.

[Lou-In-NJ]

Originally Posted by Rucksta

Check the availability of injectors and service parts before making a decision.

Yes, I've researched most of that, but as far as injectors, I see used injectors being sold on eBay, but I will look into that further since I might be told certain parts in the injector aren't serviceable and are unavailable. I will check this with a diesel service center.

As far as I can tell, all of the other items I would need are available but expensive since they are now rare. But with that said, the machine shop I use for engine work has always been able to machine aftermarket parts like valves, guides, pistons, and sleeves, for a fair price.

I can see that there comes a point, where paying 100%-200% more for old parts, just because they're rare, makes rebuilding not worth while, especially when considering my time.

[skipperpete]

I don’t have a lot of experience with MD17c’s but I have encountered leaking injector sleeves after the injectors have been removed , generally this is a dealer job, a special tool is required to “roll” the copper sleeve into the head once the new oring is installed. Its not usual to replace the whole injector, just the nozzle but as you wisely mentioned in the first post, perhaps its better to just run er! Its not broken, just a bit smoky and hard to start at times. If you pull the injectors and get a leaking sleeve, the head needs to come off (or the volvo tech comes to the boat to roll in the new sleeve and oring). The compression might be a bit low but try adjusting the valves and “Feeling” the 3 compressions by rotating the engine manually with a breaker bar and socket wrench. Maybe check er for crankase pressure too, unscrew the oil filler cap while the engine is warm and idling. The most likely cause of trouble in the future is saltwater corrosion in the waterways, it finally eats away the block and head passages to the point of no return.

[Lou-In-NJ]

Originally Posted by skipperpete

...I have encountered leaking injector sleeves after the injectors have been removed, generally this is a dealer job, a special tool is required to “roll” the copper sleeve into the head once the new oring is installed. Its not usual to replace the whole injector, just the nozzle but as you wisely mentioned in the first post, perhaps its better to just run er! Its not broken, just a bit smoky and hard to start at times. If you pull the injectors and get a leaking sleeve, the head needs to come off (or the volvo tech comes to the boat to roll in the new sleeve and oring). The compression might be a bit low but try adjusting the valves and “Feeling” the 3 compressions by rotating the engine manually with a breaker bar and socket wrench. Maybe check er for crankase pressure too, unscrew the oil filler cap while the engine is warm and idling. The most likely cause of trouble in the future is saltwater corrosion in the waterways, it finally eats away the block and head passages to the point of no return.

Just to be clear, Skipperpete, are the injector sleeves you're talking about leaking pressurized fuel, or cylinder compression?

[skipperpete]

Originally Posted by Lou-In-NJ

Just to be clear, Skipperpete, are the injector sleeves you're talking about leaking pressurized fuel, or cylinder compression?

Neither, the injector sleeves are copper and seal coolant from leaking either into the cylinder or out onto the cylinder head. They’re usually ok until disturbed by extracting the injector or being subjected to an engine overheat.

[Lou-In-NJ]

Originally Posted by skipperpete

Neither, the injector sleeves are copper and seal coolant from leaking either into the cylinder or out onto the cylinder head. They’re usually ok until disturbed by extracting the injector or being subjected to an engine overheat.

Wow. Thanks for that information!

[Lou-In-NJ]

An update on the old MD17c: it's worked great this season, we've put about 30 hours on it so far. I've been using Shell's Rotella T1 straight 30 synthetic oil, and the engine hasn't required any ether to start it. I just turn it over for about 2 seconds while pulling the decompression lever, then push in the decompression lever while continuing to crank, and it starts right up. It burns about 3 ounces of oil every 10 hours. Also, for a diesel, the oil has remained uncharacteristically clean, meaning it isn't totally black on the dipstick, it still has some of the golden color to it. I'd like to rebuild at least the top end of this engine just for my own assurance of reliability, if I can find a Bosch shop that can service the injection system, but on the other hand, it seems to be working great and if a bolt or stud breaks off in the process, I might find that I've caused a major time and expense issue that was unnecessary.